5b Sebaceous hyperplasia

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Sebaceous hyperplasia (SH) is a common benign tumor that typically occurs on the face, chiefly the forehead and cheeks, in middle age and the elderly. Either one or more, frequently multiple, elevated, small, soft, yellowish, slightly umbilicated papules are present. They exhibit telangiectatic vessels that may cause some lesions to clinically resemble basal cell carcinoma. On dermoscopic examination, SH shows a typical pattern with yellow-white central globular structures, corresponding to the hyperplastic sebaceous lobules. Distributed around these structures are prominent vessels called ‘crown vessels’ because of their morphology and distribution 1-3 ( Figure 5.21 ). These tumors appear early and in great number in the setting of immunosuppression, in familial cases, and in some genodermatoses such as Muir-Torre syndrome and pachydermoperiostosis. Histologic examination of SH finds a tumor composed of enlarged, lobulated sebaceous glands connecting to widened sebaceous ducts which empty into a central dilated follicular infundibulum commonly plugged with sebum and keratin, forming the umbilicated portion of the tumor ( Figures 5.22 , 5.23 , 5.26 ). 4 Reflectance confocal microscopy (RCM) of sebaceous hyperplasia exhibits characteristic features that correlate well with findings on dermoscopy and histology. Imaging at the level of the epidermis reveals a dilated follicular infundibulum containing a keratotic plug with sebum (Figure 5.26A-C ). In the dermis, crown vessels surrounding the duct are seen as dilated dark tubular structures containing weakly refractile round cells (erythrocytes) and brightly refractile round cells (granulocytes) (Figure 5.24 ). Occasionally, the surface of enlarged sebaceous glands can be seen at the level of the superficial dermis as morula-like clusters of round cells with glistening brightly refractile speckled cytoplasms (Figures 5.25 , 5.26C ). 5-7 RCM has been used for the monitoring of laser treatment in sebaceous hyperplasia. 5,7 Figures 5.21-5.23 Clinical photograph (inset) of sebaceous hyperplasia on the forehead of a 71-year-old patient. Dermoscopy shows pale yellow central structures (asterisks) corresponding to the sebaceous lobules and typical crown vessels (arrow). Histology (4×) shows an increased number of enlarged sebaceous glands in the superficial dermis (above) and, at a different level, the associated, plugged follicular infundibula, from which the hyperplastic sebaceous glands emanate.

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